There is a demand for electrophotographic image formation apparatus having an enhanced speed, extended longevity, and improved energy consumption. To meet this demand, toners should also be improved in various performance aspects. Extending the longevity, in particular, requires that a toner be able to develop an image even after long use. Enhancing the processing speed and energy consumption requires that the low-temperature fixation of a toner be enhanced.
As the market expands, electrophotographic image formation apparatus have been increasingly used in hot regions, such as Southeast Asia and the Near and Middle East. The storage stability of a toner at high temperatures that could be reached in such a region is becoming more and more important.
To meet these requirements, i.e., stable development for long periods of time, enhanced low-temperature fixation, and high-temperature storage stability, researchers have proposed various toners.
PTL 1 proposes stabilizing the chargeability of a toner by adding large-diameter silica as inorganic spacer particles.
PTL 2 proposes that adding crystalline resin particles to toner particles improves the low-temperature fixation of the toner. PTL 3 proposes that adding composite particles containing silica fine particle and particulate melamine to toner particles provides the toner with improved development performance, protection against image deletion, and the ease of cleaning.
PTL 4 proposes adding composite particles containing inorganic fine particles fixed on the surface of organic fine particles in order to make the toner less sensitive to its surrounding environment.
PTL 5 proposes an external additive for toners, and this external additive contains composite particles containing inorganic fine particles embedded in the surface of resin fine particles.